This invention relates to an apparatus for sensing the density variations of a textile sliver and is of the type that has a sliver funnel which combines a running web into a sliver which passes through a pressure chamber provided in the discharge portion of the sliver funnel. The pressure chamber has a lateral opening through which compressed air is supplied from a pressure source. The lateral opening further communicates with a pressure-responsive sensor which responds to pressure fluctuations in the pressure chamber, caused by density fluctuations of the sliver passing through the pressure chamber. Such pressure fluctuations are generated because, dependent upon the density of the sliver portion of the running sliver momentarily present in the pressure chamber, the air quantities absorbed by the sliver vary, thus causing alteration of the pressure in the pressure chamber. The pressure-responsive sensor generates a signal as a function of the fluctuation of the sliver density; this signal can be utilized to alter the sliver density.
A sliver control of the above-outlined type is disclosed, for example, in Lothar Simon, Pneumatische Messwertaufnahme in der Spinnereivorbereitung (Pneumatic Measurement Sensing for the Preparation of Spinning), TEXTILTECHNIK, Vol. 25, 1975, Issue 12, pages 759-764. According to this publication, the fluctuations of the pressure prevailing in the pressure chamber of a measuring nozzle (sliver funnel) are sensed by a diaphragm-type pressure-responsive sensor which generates an analog signal by affecting a lever arrangement which, in turn, cooperates with a resistance of an electric bridge circuit. The analog signal is applied to a web stretching machine for varying the cross section of the web introduced into the sliver funnel from the output of the web stretching machine.